The main focus of this paper is the optical flow computation for 2D movements of objects embedded on 3D surfaces. For spheric-shaped supports, object motion has only two degrees of liberty, thus the 3D optical flow constraint is not relevant. Constancy assumption is formulated using a suitable parametrization of the 3D surface, leading to a 2D equation. Input temporal sequence is also transformed according to the 3D surface parametrization. We build a complete 2D model, taking into account the underlying spherical surface. It has the merit to estimate at a lower cost velocity field in the temporal input sequence. In order to analyze motion computation results, we design an adapted visualization tool, instead of carrying out an inverse transformation for the velocity field. Adapted to the selected parametrization, it displays rapidly moving objects and velocity field and improves the understanding of the displayed information. We display optical flow computation results for 3D+t cell wall simulation sequences.